Answer:

A power supply is one of the most important components in a computer.  When a power supply is dead or overloaded, your entire system is dead or becomes unstalbe. A bad power supply could also cause other parts of your system to fail. As personal computers become ever more powerful, the importance of a reliable power supply is more than ever before. 

But yet the power supply is often the least appreciated due to the widespread mislabeling in wattage rating.  The wattage rating of a PC power supply is not officially certified and is self-claimed by each manufacturer. The more reputable makers advertise "True Wattage Rated" to give consumers the idea that they can trust the wattage advertised.  It is important to use a reliable power supply from a reputable maker that conforms to True-Wattage Rating so that user does not add more components to the system, with false confidence, to overload the power supply.

It's easy to tell if a power supply is working or not. However, until now it has been hard for a PC end-user to measure the quality and reliability of a power supply.  Based on the return rates and general experience we accumulated from many years of selling and servicing power supplies, we have these general observations:

• Sellers that carry True Wattage Rated power supplies are more open about disclosing the brand and model number of the power supply that they are advertising.
• Generally, the Intel/AMD/nVidia-approved power supplies weigh more than the non-vendor approved of the same wattage, confirming that vendor-approved ones are of better quality. It's possible that manufacturers only submit better models for the vendor approval process.
• The name-brand power supplies typically weigh more than the less-known, generic brands of the same wattage.  
  
• FCC approved power supplies often weigh more than those without FCC labels.